CENTURY DRILL & TOOL RE-THREAD REPAIR

Century’s Re-Thread Repair products restore damaged internal threads to their original size, helping preserve valuable parts that might otherwise need to be replaced. Precision-formed stainless-steel inserts create durable, dependable threads and help prevent future wear, seizing, and corrosion.

A stronger fix for stripped, worn, or damaged threads.

Available in SAE, Metric, and spark plug sizes for a wide range of applications.

Re-Thread Repair Installation Steps

1. Drill 
Use the drill bit specified in the kit to remove the damaged threads. Drill straight and keep the tool aligned with the original hole. Apply Century’s cutting oil (Part Number #64113) during drilling to reduce heat and help clear chips.

2. Tap 
Use the specialized STI (Screw Thread Insert) tap included in the kit to cut new threads in the hole. Apply cutting oil and turn the tap slowly. Reverse the tap periodically to break chips and ensure clean threads.

3. Install the Insert 
Place the Century thread repair insert onto the installation tool, making sure the tang (drive notch) engages with the tool slot. Thread the insert into the tapped hole until it sits ¼ to ½ turn below the surface of the material.

4. Remove the Tang 
After installation, remove the tang using the tang break-off tool, punch, or rod. The tool diameter should fit snugly inside the insert and have a square end (no chamfer). Insert the punch or rod until it rests on the tang at the bottom of the coil, hold the tool square, and strike sharply with a hammer to break the tang cleanly. For deeper holes, long-nose pliers may be needed to remove the broken tang.

Spark Plug Re-Thread Repair Installation Steps

1. Tap 
Use the piloted reamer tap included in the kit to enlarge the spark plug hole and create the required threads. Apply cutting oil and turn the tap slowly. Reverse periodically to break chips and keep the hole clean. Note: Cutting oil or grease may collect stray metal chips.

2. Clean 
Use compressed air to remove any remaining chips or debris from the hole.

3. Match 
Select a Re-Thread insert that matches the length of your spark plug threads.

4. Install 
Use the installation tool to thread the insert into the newly tapped hole, ensuring the knurled edge is positioned on top. Tap the top of the installation tool with a hammer to seat the knurling securely into the wall of the hole.

Pro Tips

Use Cutting Oil 
Always apply cutting oil when tapping to reduce friction, extend tool life, and produce clean threads.

Use the Correct Drill Size 
Successful repairs depend on using the drill size specified on the kit packaging.

Control Hole Depth 
Avoid drilling too deep, especially in blind holes, to prevent breaking through the material.

Safety and Best Practices

·         Wear eye protection during drilling, tapping, and tang removal

·         Maintain perpendicular alignment during all operations

·         Do not force tools – stop and correct misalignment immediately

·         Use proper torque values during fastener installation